Automatic determination of ascorbic acid by flame atomic absorption spectrometry

A continuous flow procedure is proposed for the indirect determination of a scorbic acid based on its reducing properties. Chromium(VI) in acid medium was injected into a ascorbic acid stream, and the Cr(VI) was reduced to Cr( III). This Cr(III) formed was retained on-line, proportionally to the ascor bic acid concentration in the sample, on a poly(aminophosphonic acid) chela ting resin, which is only selective for this oxidation state, while non-red uced Cr(VI) was determined by flame atomic absorption spectrometry. The pro posed method allows the determination of ascorbic acid in the range 0.4-20 mug ml(-1) with a relative standard deviation of 2.0% at a rate of ca. 90 s amples per hour. This method has been applied to the determination of ascor bic acid in pharmaceutical preparations and fruit juices. (C) 2001 Elsevier Science B.V. All rights reserved.